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Diffstat (limited to 'test/random_without_cast_overflow.h')
-rw-r--r-- | test/random_without_cast_overflow.h | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/test/random_without_cast_overflow.h b/test/random_without_cast_overflow.h new file mode 100644 index 000000000..000345110 --- /dev/null +++ b/test/random_without_cast_overflow.h @@ -0,0 +1,152 @@ +// This file is part of Eigen, a lightweight C++ template library +// for linear algebra. +// +// Copyright (C) 2020 C. Antonio Sanchez <cantonios@google.com> +// +// This Source Code Form is subject to the terms of the Mozilla +// Public License v. 2.0. If a copy of the MPL was not distributed +// with this file, You can obtain one at http://mozilla.org/MPL/2.0/. + +// Utilities for generating random numbers without overflows, which might +// otherwise result in undefined behavior. + +namespace Eigen { +namespace internal { + +// Default implementation assuming SrcScalar fits into TgtScalar. +template <typename SrcScalar, typename TgtScalar, typename EnableIf = void> +struct random_without_cast_overflow { + static SrcScalar value() { return internal::random<SrcScalar>(); } +}; + +// Signed to unsigned integer widening cast. +template <typename SrcScalar, typename TgtScalar> +struct random_without_cast_overflow< + SrcScalar, TgtScalar, + typename internal::enable_if<NumTraits<SrcScalar>::IsInteger && NumTraits<TgtScalar>::IsInteger && + !NumTraits<TgtScalar>::IsSigned && + (std::numeric_limits<SrcScalar>::digits < std::numeric_limits<TgtScalar>::digits || + (std::numeric_limits<SrcScalar>::digits == std::numeric_limits<TgtScalar>::digits && + NumTraits<SrcScalar>::IsSigned))>::type> { + static SrcScalar value() { + SrcScalar a = internal::random<SrcScalar>(); + return a < SrcScalar(0) ? -(a + 1) : a; + } +}; + +// Integer to unsigned narrowing cast. +template <typename SrcScalar, typename TgtScalar> +struct random_without_cast_overflow< + SrcScalar, TgtScalar, + typename internal::enable_if< + NumTraits<SrcScalar>::IsInteger && NumTraits<TgtScalar>::IsInteger && !NumTraits<SrcScalar>::IsSigned && + (std::numeric_limits<SrcScalar>::digits > std::numeric_limits<TgtScalar>::digits)>::type> { + static SrcScalar value() { + TgtScalar b = internal::random<TgtScalar>(); + return static_cast<SrcScalar>(b < TgtScalar(0) ? -(b + 1) : b); + } +}; + +// Integer to signed narrowing cast. +template <typename SrcScalar, typename TgtScalar> +struct random_without_cast_overflow< + SrcScalar, TgtScalar, + typename internal::enable_if< + NumTraits<SrcScalar>::IsInteger && NumTraits<TgtScalar>::IsInteger && NumTraits<SrcScalar>::IsSigned && + (std::numeric_limits<SrcScalar>::digits > std::numeric_limits<TgtScalar>::digits)>::type> { + static SrcScalar value() { return static_cast<SrcScalar>(internal::random<TgtScalar>()); } +}; + +// Unsigned to signed integer narrowing cast. +template <typename SrcScalar, typename TgtScalar> +struct random_without_cast_overflow< + SrcScalar, TgtScalar, + typename internal::enable_if<NumTraits<SrcScalar>::IsInteger && NumTraits<TgtScalar>::IsInteger && + !NumTraits<SrcScalar>::IsSigned && NumTraits<TgtScalar>::IsSigned && + (std::numeric_limits<SrcScalar>::digits == + std::numeric_limits<TgtScalar>::digits)>::type> { + static SrcScalar value() { return internal::random<SrcScalar>() / 2; } +}; + +// Floating-point to integer, full precision. +template <typename SrcScalar, typename TgtScalar> +struct random_without_cast_overflow< + SrcScalar, TgtScalar, + typename internal::enable_if< + !NumTraits<SrcScalar>::IsInteger && !NumTraits<SrcScalar>::IsComplex && NumTraits<TgtScalar>::IsInteger && + (std::numeric_limits<TgtScalar>::digits <= std::numeric_limits<SrcScalar>::digits)>::type> { + static SrcScalar value() { return static_cast<SrcScalar>(internal::random<TgtScalar>()); } +}; + +// Floating-point to integer, narrowing precision. +template <typename SrcScalar, typename TgtScalar> +struct random_without_cast_overflow< + SrcScalar, TgtScalar, + typename internal::enable_if< + !NumTraits<SrcScalar>::IsInteger && !NumTraits<SrcScalar>::IsComplex && NumTraits<TgtScalar>::IsInteger && + (std::numeric_limits<TgtScalar>::digits > std::numeric_limits<SrcScalar>::digits)>::type> { + static SrcScalar value() { + // NOTE: internal::random<T>() is limited by RAND_MAX, so random<int64_t> is always within that range. + // This prevents us from simply shifting bits, which would result in only 0 or -1. + // Instead, keep least-significant K bits and sign. + static const TgtScalar KeepMask = (static_cast<TgtScalar>(1) << std::numeric_limits<SrcScalar>::digits) - 1; + const TgtScalar a = internal::random<TgtScalar>(); + return static_cast<SrcScalar>(a > TgtScalar(0) ? (a & KeepMask) : -(a & KeepMask)); + } +}; + +// Integer to floating-point, re-use above logic. +template <typename SrcScalar, typename TgtScalar> +struct random_without_cast_overflow< + SrcScalar, TgtScalar, + typename internal::enable_if<NumTraits<SrcScalar>::IsInteger && !NumTraits<TgtScalar>::IsInteger && + !NumTraits<TgtScalar>::IsComplex>::type> { + static SrcScalar value() { + return static_cast<SrcScalar>(random_without_cast_overflow<TgtScalar, SrcScalar>::value()); + } +}; + +// Floating-point narrowing conversion. +template <typename SrcScalar, typename TgtScalar> +struct random_without_cast_overflow< + SrcScalar, TgtScalar, + typename internal::enable_if<!NumTraits<SrcScalar>::IsInteger && !NumTraits<SrcScalar>::IsComplex && + !NumTraits<TgtScalar>::IsInteger && !NumTraits<TgtScalar>::IsComplex && + (std::numeric_limits<SrcScalar>::digits > + std::numeric_limits<TgtScalar>::digits)>::type> { + static SrcScalar value() { return static_cast<SrcScalar>(internal::random<TgtScalar>()); } +}; + +// Complex to non-complex. +template <typename SrcScalar, typename TgtScalar> +struct random_without_cast_overflow< + SrcScalar, TgtScalar, + typename internal::enable_if<NumTraits<SrcScalar>::IsComplex && !NumTraits<TgtScalar>::IsComplex>::type> { + typedef typename NumTraits<SrcScalar>::Real SrcReal; + static SrcScalar value() { return SrcScalar(random_without_cast_overflow<SrcReal, TgtScalar>::value(), 0); } +}; + +// Non-complex to complex. +template <typename SrcScalar, typename TgtScalar> +struct random_without_cast_overflow< + SrcScalar, TgtScalar, + typename internal::enable_if<!NumTraits<SrcScalar>::IsComplex && NumTraits<TgtScalar>::IsComplex>::type> { + typedef typename NumTraits<TgtScalar>::Real TgtReal; + static SrcScalar value() { return random_without_cast_overflow<SrcScalar, TgtReal>::value(); } +}; + +// Complex to complex. +template <typename SrcScalar, typename TgtScalar> +struct random_without_cast_overflow< + SrcScalar, TgtScalar, + typename internal::enable_if<NumTraits<SrcScalar>::IsComplex && NumTraits<TgtScalar>::IsComplex>::type> { + typedef typename NumTraits<SrcScalar>::Real SrcReal; + typedef typename NumTraits<TgtScalar>::Real TgtReal; + static SrcScalar value() { + return SrcScalar(random_without_cast_overflow<SrcReal, TgtReal>::value(), + random_without_cast_overflow<SrcReal, TgtReal>::value()); + } +}; + +} // namespace internal +} // namespace Eigen |